Aleksandr Zakharchenko, a rebel commander and the prime minister of the Donetsk People’s Republic, said on Thursday that Russians, including active-duty soldiers on leave, had been fighting against Ukrainian government forces

"Mr. Zakharchenko said that 3,000 to 4,000 Russians had fought alongside separatists since the conflict erupted."

Mr. Zakharchenko, who says he has Ukrainian citizenship, took over as prime minister of the Donetsk People’s Republic this month, replacing Alexandr Borodai, a Russian. Several other Russians who had figured prominently in the rebel ranks, including the military commander Igor Strelkov, have also dropped from sight in recent weeks.

Rebel fighter poses next to a T-72 tank in Novasovsk that he has affectionately nicknamed Taniusha after his wife, Tatyana. Ukraine claim the rebels have received the tanks from Russia, but the militia say they were captured during clashes with government forces. Photo by Harriet Salem/VICE News.